Structure and defects of electrospun Fe2O3 nanofibers ALD-coated with SiO2

Porous and partially hollow silica-coated hematite nanofibers (NFs) are prepared by electrospinning (ES) and atomic layer deposition (ALD) through two synthetic routes, viz. ES/calcination/ALD or ES/ALD/calcination. The selected route and the number of ALD cycles control the final nanostructure and the coating thickness, respectively. The hierarchical NF structure, and the nature and density of the lattice defects and strain are investigated. The uncoated Fe2O3 NFs mostly have surface-related strain, attributed to oxygen vacancies/Fe2+ sites. ALD coating causes microstrain release and decrease of surface states. NFs calcined after ALD have extensive bulk strain owing to dislocations throughout the NF-grain volume.